<!DOCTYPE HTML>
<html>
<head>
  <script>
    function tweak() {
      var slot = document.createElement("slot");
      // The border shouldn't be visible, due to display: contents.
      slot.style.border = "1px solid red";
      slot.style.color = "green";

      var shadowRoot =
        document.getElementById('outer').attachShadow({mode: 'open'});
      shadowRoot.appendChild(slot);
    }
  </script>
</head>
<body onload="tweak()">
<div id="outer">This text should be green</div>
</body>
</html>
